add metric cup and increase precision

units.sql

@@ -6,7 +6,9 @@ CALL insert_unit ('tsp (US)');
 CALL insert_unit ('Cup (US)');
 CALL insert_unit ('Quart (US)');
 CALL insert_unit ('Gallon (US)');
+CALL insert_unit ('Cup (metric)');
 -- using customary cup as per https://en.wikipedia.org/wiki/Cup_(unit)
+CALL insert_unit_conversion ('Cup (metric)', 'mL', 250);
 CALL insert_unit_conversion ('Cup (US)', 'mL', 236.5882365);
 CALL insert_unit_conversion ('Cup (US)', 'Tbsp (US)', 16);
 CALL insert_unit_conversion ('Cup (US)', 'tsp (US)',  48);
@@ -20,12 +22,15 @@ $$
 DECLARE
   item record;
   msg text;
-  expected numeric(14,7);
-  result numeric(14,7);
+  expected numeric(20,10);
+  result numeric(20,10);
 BEGIN
   FOR item IN SELECT * FROM (VALUES
       ('L', 'mL', '', 1000), -- *
       ('mL', 'L', '', 1.0/1000),
+      ('Cup (metric)', 'mL', '', 250), -- *
+      ('L', 'Cup (metric)', '', 4),
+      ('Cup (US)', 'Cup (metric)', '', 236.5882365/250),
       ('Cup (US)', 'mL', '', 236.5882365),
       ('mL', 'Cup (US)', '', 1/236.5882365), -- *
       ('L', 'Cup (US)', '', 1000/236.5882365),